Resonator for electromagnetic waves of the millimetric and submillimetric band

ABSTRACT

A resonator for electromagnetic waves of the millimetric and submillimetric band, comprising main reflectors in the form of mountings wherein parallel conductors are strung at a spacing smaller than the length of electromagnetic waves in the selected band, and at least one additional reflector identical to, and disposed between, said main deflectors, the plane of said additional reflector being parallel to the planes of the main reflectors.

United States Patent Vinogradov et al.

[151 3,676,8 [451 July 11,1!

[54] RESONATOR FOR ELECTROMAGNETIC WAVES OF THE MILLIMETRIC ANDSUBMILLIMETRIC BAND [72] Inventors: Evgeny Alexandrovich Vinogradov,Kozhevnicheskaya ulitsa, lb, kv. 33; Nataliya Alexandrovna Irisova,ulitsa Vavilova, 44, korpus 4, kv. 74, both of Moscow, U.S.S.R.

[22] Filed: June 29,1970

[21] Appl.No.: 50,428

[52] US. Cl. ..333/83, 330/4.5, 324/58, 356/1 12 [51] Int. Cl. ..H01p7/06 [58] Field ofSearch ..333/83; 330/4.5,4.5 G; 350/160 [56]References Cited UNITED STATES PATENTS 3,187,270 6/1965 Kogelnik et al...333/83 X 3,316,511 4/1967 Schulten.... .....333/83 X 3,487,230 12/1969Costich ..330/4.5 X

3,055,257 9/1962 Boyd et al. ..333/l 3,201,709 8/1965 Boyd ..33(

3,530,301 9/1970 Boyd et a1. ..330/4 OTHER PUBLICATIONS High ResolutionMillimeter Wave Fabry- Perot 1| ferometer by Culshaw, 3/60, pp. 183-189, IRE Trans'ac on Microwave Theory and Techniques.

Resonators for Millimeter and Submillimeter Wavelengt BY Culshaw, 3/61,pp. 136- 144, IRE Transaction Microwave Theory and Techniques, Vol. 9,No. 2.

Primary Examiner-Herman Karl Saalbach Assistant Examiner-SaxfieldChatmon, Jr. AnomeyWaters, Roditi, Schwartz & Nissen ABSTRACT Aresonator for electromagnetic waves of the millimetric submillimetricband, comprising main reflectors in the for: mountings wherein parallelconductors are strung at a spa smaller than the length ofelectromagnetic waves in selected band, and at least one additionalreflector ident to, and disposed between, said main deflectors, theplan: said additional reflector being parallel to the planes of mainreflectors.

3 Claims, 2 Drawing Figures RESONATOR FOR ELECTROMAGNETIC WAVES OF THEMILLIMETRIC AND SUBMILLIMETRIC BAND The present invention relates toradio measuring techniques, and, more particularly to resonance devices,and can be employed for filtration of electromagnetic waves inmillimetric and submillimetric bands and for stabilization and frequencycalibration of the sources which radiate such waves.

There exist resonators similar to a F abry-Perot interferometeremploying flat reflectors in the form of mountings wherein conductorsare strung parallel to one another, the shortest spacing L between theconductors being smaller than the length of electromagnetic waves in theselected band.

The planes of the reflectors are parallel to each other andperpendicular to the optical axis.

However, the existing resonators of millimetric and submillimetricwavebands have essential disadvantages. One of such disadvantages liesin the fact that the shape of the resonance curve of such a resonator isanything but rectangular, and this is especially undesirable when theresonator is to be used as a filter.

Besides, the attempt to increase the Q of the resonator by placing thereflectors at greater distances from each other results in the increasednumber of resonant frequencies in the natural frequency spectrum of theresonator, which may affect the quality of filtration or the frequencyoutput of the oscillator being stabilized.

The use of a two-reflector resonator for marking equidistant frequencieson a small scale makes it rather difficult directly to find the absolutevalue of the frequency.

An object of the present invention is to provide a multiplecoupledresonator for electromagnetic waves of the millimetric andsubmillimetric bands.

With this object in view, a resonator for electromagnetic waves of themillimetric and submillimetric band, in which reflectors are in the formof mountings with parallel conductors, the shortest spacing betweenwhich is smaller than the length of electromagnetic waves in theselected band, comprises, according to the present invention, at leastone additional reflector, identical to, and disposed between, saidreflectors, the plane of said additional reflector being parallel to theplanes of the main reflectors.

It is preferable to make at least one additional reflector or capable ofdisplacement. v

[t is possible to make at least one of the main reflectors capable ofdisplacement.

The present invention will be best understood from the followingdetailed description of its embodiment when read in connection with theaccompanying drawings, in which:

FIG. 1 is a view showing the arrangement of reflectors in amultiple-coupled resonator;

FIG. 2 shows an embodiment of the reflector.

A multiple-coupled resonator for electromagnetic waves of themillimetric and submillimetric band comprises at least three reflectors1, 2 and 3 (FIG. 1), the planes of which are parallel to one another andperpendicular to their common optical axis. The reflectors disposed asabove form two coupled resonators l and Il.

Each reflector (FIG. 2) is a mounting 4 which may be shaped as ringwherein conductors 5 are strung parallel to one another.

To reduce diffraction losses the diameter a of the mounting 4 is madegreater than the maximum wavelength A of the selected band. The higherthe ratio a/ A, the greater the Q of the resonator and the more strictlyequidistant is the distribution of the natural frequencies of theresonator.

To reduce the losses caused by the resistance of the conductors 5 andincrease the Q and the resonant oscillation amplitude of the resonatorthe conductors 5 strung in the mount ing 4 must be made from a materialpossessing the highest possible conductance or a coating must be usedthe thickness of which is not smaller than the skin layer for theselected.

band.

The conductors 5 may have a section of any geometrical shape though aroundsection is preferable.

A spacing 1 between the conductors 5 must be smaller the the maximumwavelength in the selected band. The greatt the ratio Ale and d/e,"where d is the width of the CO1 ductor in the plane of the mounting, thegreater is the Q of ti resonator. However, this is true only so long asthe 1055! caused by the resistance of the conductors do n predominate.

In a multiple-coupled resonator (FIG. 1) the Q of th resonator and theamount of coupling between separal resonators I and II may vary with thegeometrical parameter of separate reflectors l, 2 and 3 (the diameter ofthe refle tors, spacing between the conductors, section and size of thconductors) or, for the given geometrical parameters, with th angle bywhich the reflectors are turned with respect to th optical axis.

The resonant frequencies common to the two resonators and II can beselected by varying the distance from the add: tional reflector 2 toeither of the main reflectors.

This makes it possible to considerably space out the nature frequencyspectrum of the first resonator or intensify resonan frequenciesmultiple of some integral number to provid frequency marks of a greaterscale.

To provide reference scale marks the reflectors 1,2 and are spaced atdefinite distances by means of calibrated inserts for arbitraryselection of scales at least two reflectors may b provided with devicesfor their displacement and accurat measurement of their relativeposition (the inserts and th measuring devices are not shown in thedrawing).

The resonator operates as follows.

The electromagnetic radiation generated by a source 6 o millimetric andsubmillimetric waves is directed by a radiatin; aerial along the axis ofthe resonator onto a reflector 1 tht aerial is not shown in thedrawing).

Part of the electromagnetic flux is reflected from the reflec tor 1 andthe remainder of the flux reaches the resonator 1 Owing to the presenceof coupling between the resonators and II the electromagnetic flux thenreaches the resonator l and leaves this resonator through a reflector 3.The ratir between the part of the electromagnetic flux that is reflectetfrom the resonator and the part that passes through it depend: onwhether the resonators l and [I are tuned to the frequenc of radiationgenerated by the source of electromagnetk waves, on the amount ofcoupling between the resonators am on the transmission of the reflectorsl and 3.

The part of the electromagnetic flux passing through themultiple-coupled resonator is picked up bya radiatior receiver 7disposed behind the reflector 3.

The source 6 of electromagnetic radiation, the multiple coupledresonator and the radiation receiver 7 are all alignec along one opticalaxis.

The part of the electromagnetic flux reflected from the reflector 1 canbe picked up by an additional radiatior receiver 8, the axis of which isperpendicular to the main optical axis. The part of the electromagneticflux reflected frorr the reflector l is directed onto this additionalreceiver by z semi-transparent mirror 9 disposed between themultiple-coupled resonator and the source 6 of electromagnetic radiatiorso that the plane of the mirror is at an angle of 45 to the mair opticalaxis.

Let us see how the magnitude of the signal reflected frorr themultiple-coupled resonator varies if all three reflectors l 2 and 3 havethe same geometrical dimensions, and the conductors of the reflectors l,2 and 3 are parallel to one another and to the intensity vector E of theelectric field.

As was mentioned above, a greater part of the flux will be reflectedfrom the resonator I if this resonator is tuned to the frequency of theincident radiation.

If the resonator l is tuned to the radiation frequency while theresonator II is not tuned to this frequency part of the incidentelectromagnetic flux is absorbed in the resonator l and the reflectedpart of the electromagnetic flux diminishes. if the resonator l is tunedto the same frequency as the resonator ll. the reflected part of theelectromagnetic flux becomes greater.

This property of the resonator is used to provide calibration frequencymarks when the source 6 of electromagnetic waves operates in frequencyscanning mode.

In this case the spacing between the reflectors 2 and 3 is made severaltimes smaller than the spacing between the reflectors l and 2.

As a result the spacing between the natural frequencies of the resonator11 becomes several times greater than the spacing between the naturalfrequencies of the resonator I, and the frequency marks of the resonatorl coinciding with the natural frequencies of the resonator II will havea much smaller amplitude in the reflected signal than all other marks,or will disappear altogether.

The amplitude of the marks obtained as above can be adjusted by turningthe reflector 3 about its axis. To facilitate measurement of thereflected signal the last reflector can be substituted with a solidmirror having a flat or spherical surface.

The multiple-coupled resonator described herein is also a convenientmeans for measuring refractive index of various substances, when thethickness of the test specimen (in the case of hard specimens)considerably exceeds the wavelength of electromagnetic radiation.

The operating procedure is as follows.

The two resonators l and II are adjusted so that their resonantfrequencies coincide, then a test specimen is placed in one of theresonators and the resonant frequencies of the resonators are gaincaused to coincide by displacing one of the end reflectors l or 3.

The distance by which one of these reflectors has to be displacedrepresents the difference in the beam travel caused by the specimen.Knowing this difference one can easily calculate the refractive index ofthe specimen.

If the only object is to make the resonance curve of the resonator asnearly rectangular as possible the second resonator ll may be tuned tothe same frequencies as the first one.

If the object is to space out the natural frequencies of the firstresonator I, the spacings L and L between the reflectors 1, 2 and 3 ofthe resonators l and ll are made multiple of M2 only for thosewavelengths which are to be left in the frequency spectrum.

What is claimed is:

1. A resonator for electromagnetic waves of the millimetric andsubmillimetric band, comprising main reflectors and at least oneadditional reflector, the plane of said additional reflector beingparallel to the planes of said main reflectors, said reflectors havingmountings and conductors strung in the mountings parallel to oneanother, the shortest spacing between said conductors being smaller thanthe length of electromagnetic waves in the selected band.

2. A resonator as claimed in claim 1, comprising at least one additionalreflector capable of displacement.

3. A resonator as claimed in claim 1, comprising at least one mainreflector capable of displacement.

1. A resonator for electromagnetic waves of the millimetric andsubmillimetric band, comprising main reflectors and at least oneadditional reflector, the plane of said additional reflector beingparallel to the planes of said main reflectors, said reflectors havingmountings and conductors strung in the mountings parallel to oneanother, the shortest spacing between said conductors being smaller thanthe length of electromagnetic waves in the selected band.
 2. A resonatoras claimed in claim 1, comprising at least one additional reflectorcapable of displacement.
 3. A resonator as claimed in claim 1,comprising at least one main reflector capable of displacement.